A breathing assistance device typically delivers pressurized breathing gas to a patient via tubing called a “patient interface” or a “breathing circuit.” The breathing gas typically includes air and/or one or more gasses (e.g., oxygen mixed with the air). The breathing gas delivered to the patient from the breathing assistance device may be humidified and/or heated in the breathing circuit before being delivered to the patient. The breathing assistance device typically increases the pressure in the breathing circuit so that the breathing gas is pushed into the lungs for inspiration, and reduces the pressure in the breathing circuit so that gases in the lungs can be expired and vented to the atmosphere. Typically, one or more breathing assistance device parameters may be determined and/or adjusted prior to and/or during operation, e.g., the mode of ventilation (e.g., CMV (controlled mandatory ventilation), SIMV (synchronized intermittent mandatory ventilation), CPAP (constant positive airway pressure), or bi-level CPAP); the patient's tidal volume (the volume of gas inspired with each breath); the respiratory rate (the number of breaths per minute (BPM)); and/or the O2 concentration, flow rate, airway pressure, and/or minute volume (the volume inspired and expired in one minute) of breathing gas delivered to the patient.
Operational faults may occur in breathing assistance devices from time to time. For example, a fault within a source of pressurized gas flow (or a “gas flow source”) associated with a breathing assistance system, e.g., a blower, compressor, or a piston-based device, may occur. While such a fault may inhibit operation of the gas flow source, electrical current to the proper gas flow source may continue, potentially causing the gas flow source to overheat, cause injury to the patient or cause a fire (possibly leading to expensive damage to the breathing assistance device), or even cause an explosion (possibly leading to injury to a patient or other person). As a further example of a potential fault, a portion of a patient interface (e.g., a patient mask, nasal pillows, or an air tube) associated with a breathing assistance device may become disconnected from the patient and/or the breathing assistance device. In some instances, such a disconnection may cause a control circuit associated with the breathing assistance device to erroneously detect that the airway pressure being delivered to the patient is too low, and the control circuit may increase the pressure and/or flow of gas provided to the patient, which may, e.g., cause mechanical stresses within the breathing assistance device, and/or waste of electrical power. In addition, other faults may occur within a breathing assistance system that may be detected using some or all of the methods and systems herein disclosed.